Assigning uplink slots to optimize uplink power control gain in wireless communications

ABSTRACT

A method and system for assigning uplink (UL) slots to optimize time division duplex (TDD) UL power. In order to assure proper power control gain, UL slots are judiciously allocated close to the beacon slot. The UL slots may be allocated based on channel sensing. All users are sorted in the order of reducing fading losses. Sorting information is also used to allocate the UL slots. The UL slots may also be allocated based on signal interference information, code usage availability estimates and spread signal interference values. Alternatively, block error rate (BLER) and signal to interference ratio (SIR) measurements may be used to allocate the UL slots.

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority from U.S. provisionalapplication No. 60/427,907, filed Nov. 20, 2002, which is incorporatedby reference as if fully set forth.

FIELD OF THE INVENTION

[0002] The present invention relates to spread spectrum communicationsystems. More particularly, the present invention relates to a systemand method for allocating uplink (UL) slots to control transmissionpower within time division duplex (TDD) communication systems.

BACKGROUND

[0003]FIG. 1 depicts a wireless spread spectrum TDD communication system100. The system 100 has a plurality of base stations 30 ₁-30 ₇. Eachbase station 30 communicates with a plurality of wirelesstransmit/receive units (WTRUs) in its operating area. For example, basestation 30 ₁ communicates with WTRUs 32 ₁-32 ₃. Communicationstransmitted from a base station 30 to a WTRU 32 are referred to asdownlink communications, and communications transmitted from a WTRU 32to a base station 30 are referred to as uplink communications.

[0004] In a Universal Mobile Telecommunications System (UMTS) asspecified by the Third Generation Partnership Project (3GPP), basestations are called Node Bs, subscriber stations are called wirelesstransmit/receive units (WTRUs) and the wireless CDMA (Code DivisionMultiple Access) interface between the Node Bs and UEs is known as theUu interface.

[0005] Node Bs are typically capable of conducting wireless concurrentcommunications with a plurality of subscriber stations, genericallyknown as WTRUs (i.e., User Equipments (UEs)), which include mobileunits.

[0006] In addition to be able to communicate over different bands offrequency spectra, spread spectrum TDD systems can carry multiplecommunications over the same band of frequency spectra. Individualcommunication signals are distinguishable by their respective chip codesequences (codes). FIG. 2 shows two frames 34A, 34B of a TDD signal 200.Each frame 34A, 34B is divided into 15 time slots 36 ₁-36 ₁₅. In suchsystems, a communication is sent multiplexed in selected time slots 36₁-36 ₁₅ using codes. Accordingly, one repeating frame 34 is capable ofcarrying multiple communications distinguished by both time slot andcodes. The combination of a single code in a single time slot isreferred to as a resource unit. One or multiple resource units areassigned to a communication based on the bandwidth required to supportthe communication.

[0007] Most TDD systems adaptively control transmission power levelsallowing many base stations and WTRUs to share the same time slotswithin a radio frequency spectrum. For example, when WTRU 32 ₁ isreceiving a specific communication from base station 30 ₁, all the otherWTRUs and base stations communicating using the same time slots andspectrum will generate interference on the downlink communication ofbase station 30 ₁.

[0008] One way for base station 30 ₁ to ensure delivery of informationis by increasing the transmission power level. However, this willdegrade the signal quality of all other communications within that timeslot and radio frequency spectrum by generating interference. To avoidincreasing power of the base station 30 ₁, all the other WTRUs and basestations within range may be instructed to decrease their transmitpower. However, reducing the transmission power level of these basestations and WTRUs too far, will result in undesirable signal to noiseratios (SNRs) and high bit error rates (BERs) at the receivers.

[0009] To maintain both the quality of communications while controllingthe transmission power levels, a transmission power control scheme isused. This is especially important on uplink situations where a near-farproblem may occur. The near-far problem occurs when a base station (BS)receives a much stronger signal from a WTRU nearby than from anotherWTRU far away. Since all users share the same frequency band, the nearWTRU would drown out the far WTRU. In addition, power control alsoprolongs battery life while it reduces interference.

[0010] One approach using transmission power control in a code divisionmultiple access (CDMA) communication system is described in U.S. Pat.No. 5,056,109 (Gilhousen et al.). A transmitter sends a communication toa particular receiver. Upon reception, the received signal power ismeasured. The received signal power is compared to a desired receivedsignal power. Based on the comparison, a control bit is sent to thetransmitter either increasing or decreasing transmission power by afixed amount. Since the receiver sends a control signal to thetransmitter to control the transmitter's power level, such power controltechniques are commonly referred to as closed loop.

[0011] Under certain conditions, the performance of a closed loop systemwill degrade. For example, if communications sent between a WTRU and abase station which are in a highly dynamic environment, such as due tothe WTRU moving, such systems may not be able to adapt fast enough tocompensate for the changes. The update rate of closed loop power controlin TDD is typically 100 cycles per second which is not sufficient tocompensate for fast fading channels. For example, a WTRU traveling at100 kilometers per hour (62 miles per hour) may travel 278 centimetersbetween updates. In addition, if the WTRU were operating at 881.52 Mhz,the distance traveled between updates would be approximately 294 degreesof a wavelength and may place the WTRU into a deeper null.

[0012] Outer loop and weighted open loop power controls are othermethods for transmission power control. Outer loop power controlutilizes an error detection device to look at the soft symbols anderrors produced in a data estimation device. A processor analyzes thedetected errors and determines an error rate for the receivedcommunication. Based on the averaged error rate, a processor determinesa desired target error rate for the communication. The processordetermines an amount, if any, the power level needs to be changed at thetransmitting station to achieve the desired error rate. An adjustment issubsequently sent to the transmitting station using a dedicated or areference channel.

[0013] To compound the fading problem, a WTRU employing a time slotwhich is located temporally distant from the reference beacon time slotmay reposition itself during this time interval and may move into adeeper null resulting in a deeper fade. For example, a WTRU using timeslots in the middle of a standard frame having the fixed length of 10 mswill allow the WTRU to travel an additional one-half wavelength at 108km/hr. In addition to moving in and out of nulls, the WTRU by itsmovement introduces Doppler fading into the mix. These affects are morepronounced in systems which have less frequent power controladjustments.

[0014] Therefore, compensating for deep fading and Doppler frequency andphase shifting are important to power control gain. In addition tofading and Doppler, the time slot separation between the referencebeacon and the WTRU's time slot also has an impact on efficient powercontrol gain. This is especially pronounced in the TDD mode ofoperation. Consequently, it is desirable to have a method to choose slotlocations to optimize uplink power control gain with fading channelswhile taking into account Doppler effects.

SUMMARY

[0015] The present invention provides a method of optimizing uplink (UL)channel power control gain based on channel sensing and the slotseparation between a beacon channel and the allocated slot channelwithin the UL frame of a WTRU. Channels are allocated such that thepower control gain is maximized for those channels that require it most.The benefit of judicious channel allocation allows for an increase inthe average power control gain, which results in enhanced cell coverageand capacity.

[0016] The present invention allocates as many UL slots as practicalnear the beacon channel(s) providing all WTRUs within the communicationsystem the benefit of a higher power control gain. A WTRU with UL slotscloser to the beacon(s) will not be able to travel as far as slotsfurther from the beacon. This is because there is a larger time lag withUL channels further from the beacon. The present invention may beincorporated into an integrated circuit (IC) or be configured in acircuit comprising a multitude of interconnecting components.

[0017] In one embodiment, all the WTRUs are sorted in reduced order ofestimated fading losses. The sorting information is then taken intoaccount when allocating slots such that users with higher fading losseswill be allocated closer to the beacon(s). The fading loss estimates maybe performed at the node B directly from the channel estimates and theinformation transmitted to the controlling radio network controller(CRNC).

[0018] In an alternative embodiment, a block error rate (BLER) will becontrasted to a signal to interference ratio (SIR) measurement producinga gauge of the fading. For example, a generally higher BLER for same SIRwould indicate deeper fading. The information is readily available atthe serving radio network controller (SRNC) as part of the outer looppower control and may be forwarded to the CRNC. The CRNC information maybe combined with other information such as slot interference and codeavailability to decide the optimal slot positioning.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] A more detailed understanding of the invention may be had fromthe following description of a preferred example, given by way ofexample and to be understood in conjunction with the accompanyingdrawings wherein:

[0020]FIG. 1 illustrates a prior art TDD system;

[0021]FIG. 2 illustrates time slots in repeating frames of a TDD system;

[0022]FIG. 3 is a block diagram of a slot allocation system operating inaccordance with the present invention;

[0023]FIG. 4 is a flow chart of a process using signal interference,code usage availability estimates and spread spectrum interferenceinformation to assign a slot in accordance with a first embodiment ofthe present invention; and

[0024]FIG. 5 is a flow chart of a process using BLER and SIR to assign aslot in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] In a Universal Mobile Telecommunications System (UMTS) asspecified by the Third Generation Partnership Project (3GPP), basestations are called Node Bs, subscriber stations are called UEs and thewireless code division multiple access (CDMA) interface between the NodeBs and UEs is known as the Uu interface.

[0026] Node Bs are typically capable of conducting wireless concurrentcommunications with a plurality of subscriber stations, (i.e., WTRUs),which include mobile units. Generally, the term base station includesbut is not limited to a base station, Node-B, site controller, accesspoint or other interfacing device in a wireless environment. The termwireless transmit/receive unit (WTRU) includes but is not limited to auser equipment, mobile station, fixed or mobile subscriber unit, pageror any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, a base station includes but isnot limited to a base station, Node-B, site controller, access point orother interfacing device in a wireless environment.

[0027] Although the preferred embodiments are described in conjunctionwith a third generation partnership program (3GPP) code divisionmultiple access (CDMA) system utilizing the TDD mode, the embodimentsare applicable to any hybrid CDMA, time division multiple access (TDMA)communication system.

[0028] The present invention will be described with reference to thedrawing figures wherein like numerals represent like elementsthroughout. A repeating frame 34 of with time slots 36 ₁-36 ₁₅ of a TDDsystem is illustrated in FIG. 2. The first slot 36 ₁ represents a beaconchannel and is used as the pathloss (or channel condition) measurementslot. A WTRU will receive and take measurements of the beacon channel.The WTRU will make uplink reports of the measurements to the node B andthe node B will make power adjustments accordingly. It should be notedthat the system may also designate other slots as the power controlslots.

[0029] To better understand the present invention, an outer loop powercontrol equation will first be discussed to show the importance ofbeacon to slot location allocation. An example of an equation to derivea transmitting station's transmission power is depicted as per Equation1:

P _(TS) =SIR _(TARGET) +I _(RS)+α(L−L ₀)+L ₀+CONSTANT_VALUE  Equation 1

[0030] where P_(TS) is transmission power level in decibels,SIR_(TARGET) is the target signal to interference ratio, which is avalue determined on received target adjustment signals, I_(RS) is themeasure of the interference power level at the receiving station, α is aweighting measure of the quality of the estimated path loss and is basedon the number of time slots between the time slot of the last pathlossestimate and the first time slot of the communication transmitted by thetransmitting station, L is a path loss estimate in decibels, L₀ is thelong term average of the path loss in decibels and is the runningaverage of the pathloss estimate L and CONSTANT_VALUE is a correctionterm which corrects for differences in the uplink and downlink channels.

[0031] The weighting value of α plays an import factor in the powercontrol algorithm and is assigned a value between zero and one.Generally, if the time difference between the reference beacon and theassigned time slots is small, the recent path loss estimate will befairly accurate and α is set at a value close to one. By contrast, ifthe time difference is large, the path loss estimate may not beaccurate. Accordingly, α is set at a value closer to zero and isdetermined as per Equation 2:

α=1−(D−1)/(D _(max)−1)  Equation 2

[0032] where the value, D, is the number of time slots between the timeslot of the last path loss estimate and the first time slot of thetransmitted communication, which is referred to the time slot delay.D_(max) is the maximum number of possible delay slots. If the time slotdelay is one time slot, α is one for any size frame. However, if a framehas 15 slots and beacons in slots k and k+8, the maximum number of slotsa WTRU can transmit its uplink from a beacon is seven. Table 1 shows thecalculated α values for such a 15 slot frame. TABLE 1 Slots away frombeacon 1 2 3 4 5 6 7 α value 1 .83 .66 .5 .33 .166 0

[0033] As shown in Table 1, the α calculation for slots closer to thebeacon's transmission use a truer representation of the WTRU's path lossestimate. WTRUs that are assigned slots further from the beacon willhave more time to move before sending back power or signal qualityinformation on a earlier received beacon. As stated above, the WTRU mayhave repositioned itself into a deep null or peak, thus discounting thecurrent path loss estimate and subsequent power correction.

[0034]FIG. 3 is a block diagram of a system 300 which implements a slotallocation process. The system 300 includes an interference informationdevice 302, a code usage estimator device 304, a fading loss estimatordevice 306, weighting devices 308, 310, 312, multipliers 303, 305, 307,summer 314, slot ranking device 316 and slot prioritization device 318.Each of multipliers 303, 305 and 307 has two inputs and one output. Thesystem 300 may be located within the CRNC.

[0035] The signal interference information device 302 is connected toone of the inputs of multiplier 303. The other input of the multiplier303 is connected to weighting device 308. The output of the multiplier303 is connected to a first input of summer 314.

[0036] The code usage estimator device 304 is connected to one of theinputs of multiplier 305. The other input of the multiplier 305 isconnected to weighting device 310. The output of the multiplier 305 isconnected to a second input of summer 314.

[0037] The fading loss estimator device 306 is connected to one of theinputs of multiplier 307. The other input of the multiplier 307 isconnected to weighting device 312. The output of the multiplier 307 isconnected to a third input of summer 314. The output of summer 314 isconnected to the slot ranking device 316. The output of the slot rankingdevice 316 is connected to the slot prioritization device 318.

[0038] The signal interference information device 302 contains datasupplied by interference measuring devices, such as interference signalcode power (ISCP) or other time slot/system interference measurements.The code usage estimator device 304 maintains an indication, such as apseudo image, of the CRNC's slot resource allocation database. Thefading loss estimator device 306 operates as a function of the SIR andthe desired BLER. For example if it is known that at a certain symbollevel has a SIR of 2.5 dB, which is sufficient to obtain a BLER of 0.01,the losses can be defined as the difference between the actual requiredSIR and that number. The number of samples used to determine the fadingloss is preferably a design parameter and would have to be found inextensive simulations or empirical trials

[0039] The weighting devices 308, 310, 312 are applied to the signalinterference information 302, the usage availability estimator 304 andthe fading loss estimator 306, respectively, via multipliers 303, 305,307. The weighting values can be determined by simulation, empiricallyor by other means. The weighting devices 303, 305, 307 allow anadministrator of system 300 to tweak the parameters of the system 300for optimum performance. The values of the weighting devices 308, 310,312 are added by summer 314. The slot ranking device 316 ranks the slotsaccording to their combined score. The slot prioritization device 318then assigns slots having higher priority to slot locations nearest tothe reference beacon. The slots with lower priority are assigned to slotlocations further away from the reference beacon.

[0040]FIG. 4 is a flow diagram of a process 400 implementing methodsteps in accordance with one embodiment of the present invention. Instep 405, a present WTRU is activated within the system. In step 410, aninitial slot assignment is made for the present WTRU. In step 415,signal interference information associated with the present WTRU iscollected. In step 420, the present code usage and available estimatesof code usage associated with the present WTRU are collected. In step425, the wireless radio channel spread values associated with thepresent WTRU are collected, the spread values indicating how much thepaths of a given wireless channel are spread in time and/or frequencyto, for example, produce the estimated fading loss. In step 430, thesignal interference, code usage and spread values are each multiplied bya respective weight value (weight 1, weight 2, weight 3), resulting inthree weighted products. In step 435, the weighted products are summedtogether. In step 440, the result of step 435 is compared to the resultsof summed weighted products associated with other WTRUs and the presentWTRU is ranked accordingly. In step 445, the present WTRU is thenassigned a slot based upon the rank determined in step 440.

[0041] In another embodiment, it is possible for the Node-B to estimatethe channel coefficients directly. This is due to the fact that thespread of the channel corresponds to the channel losses. Therefore, ameasure of the spread can be used in producing the fading loss estimate.For example, the smaller the path spread of the channel, the greater thechannel loss.

[0042] It is also possible to use the Node B to measure Doppler anddetermine a fading rate, which may also be used for fading lossestimates. A high Doppler value corresponds to deep fading andconversely, a lower Doppler rate corresponds to a more shallow fading.The higher the Doppler rate, the faster the fading rate, i.e., morechannel power fluctuation. Faster fading may take a small fraction ofthe interleaving interval, in which case its effect on the BLER isreduced.

[0043]FIG. 5 is a flow diagram of a process 500 implementing methodsteps in accordance with another embodiment of the present invention. Instep 505, a WTRU is activated within the system. In step 510, an initialslot assignment is made for the WTRU. In step 515, a channel impulseresponse is estimated from each random access channel (RACH) access. Instep 520, a spread value provides an estimate of the initial fading. Instep 525, the system attempts to improve or enhance the estimate toenhance the slot assignment. In step 530, the system examines the BLERand SIR values. In step 535, a determination is made as to whether theBLER and SIR values are high. If yes, the system assigns the WTRU'suplink slot closer to the beacon in step 540 and returns to step 525. Ifthe BLER and SIR values are not high, the system will return to step525.

[0044] In yet another embodiment, a method for sorting all the WTRUs byα in a coverage area is disclosed. After sorting, the WTRUs areallocated time slots in order to reduce the system's overall fadinglosses and increase system capacity. A CRNC may allocate all time slotsby assigning each WTRU a α value between zero and one. A α of onerepresents the maximum value of the weighting parameter used in the WTRUpower calculation. The α information may be individually signaled toeach WTRU. WTRUs with a higher value of beta will be assigned channelscloser to the reference beacon.

[0045] An additional indicator for fading losses may include vehicularWTRU speed. A direct correlation exists between high WTRU's speed andthe worsening multipath fading. Therefore, a high speed WTRU would beindicative of deeper fading.

[0046] In a variation of the above embodiment, other parameters thatcontrol UL slot location/allocation may include information other thanthe beta information in this variation of the present invention. Forexample, WTRUs having a small α value of less than 0.5 will not benefitfrom higher power control gain even if assigned slots closer to thebeacon. In this case, the WTRUs with the larger α values should becloser to the beacon. The α information can be also used as one of thecriteria or it can be combined with other criteria, e.g., fading, todetermine the optimal UL slot allocation.

[0047] In yet another embodiment, a Doppler measurement is utilized. Ameasurement would be generated by either the channel impulse rate ofchange or BLER versus the raw BER. The channels with Doppler rates thatfall into a median range would be placed nearer the Beacon. Conversely,channels with very high Doppler rates would be placed far from thebeacon as they will typically not benefit significantly from powercontrol. Different methods of measuring fading losses may be used inaccordance with the present invention.

[0048] While this invention has been particularly shown and describedwith reference to preferred embodiments, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the scope of the invention describedhereinabove.

What is claimed is:
 1. A method for controlling transmission powerlevels of signals in a spread spectrum time division duplex (TDD)communication system, the signals having frames with time slots forproviding a communication, the method comprising: (a) a firstcommunication station transmitting a first signal having a transmissionpower level in a first time slot; (b) a second communication stationreceiving the first communication and measuring a plurality of signalquality parameters of the first communication; (c) determining a slotassignment rank for the first communication station based on theplurality of signal quality parameters; and (d) assigning a second timeslot to the first communication station for subsequent communications.2. The method of claim 1 wherein the plurality of signal qualityparameters include at least one of the following values: a weightedsignal interference information value, a weighted code usage estimationvalue and a weighted fading loss estimation value.
 3. The method ofclaim 2 further comprising: (e) prioritizing a plurality of wirelesstransmit/receive units (WTRUs) currently communicating via acommunication network; and (f) assigning each of said plurality of WTRUsa slot assignment based upon the slot assignment rank.
 4. The method ofclaim 1 wherein the first communication station is a base station (BS)and the second communication station is a wireless transmit/receive unit(WTRU).
 5. The method of claim 1 wherein the first communication stationis a wireless transmit/receive unit (WTRU) and the second communicationstation is a base station (BS).
 6. The method of claim 1 wherein theplurality of signal quality parameters include at least one of thefollowing values: a block error rate (BLER) value and a signal tointerference ratio (SIR) value.
 7. A method for controlling transmissionpower levels of signals in a spread spectrum time division duplex (TDD)communication system, the signals having frames with time slots forproviding a communication, the method comprising: (a) a firstcommunication station transmitting a first signal having a transmissionpower level in a first time slot; (b) a second communication stationreceiving the first communication and measuring a plurality of signalquality parameters of the first communication, the parameters includingat least one of a block error rate (BLER) value and a signal tointerference ratio (SIR) value; (c) determining a slot assignment rankfor the first communication station based on the parameters; and (d)assigning a second time slot to the first communication station forsubsequent communications.
 8. The method of claim 7 further comprising:(e) prioritizing a plurality of wireless transmit/receive units (WTRUs)currently communicating via a communication network; and (f) assigningeach of said plurality of WTRUs a slot assignment based upon the slotassignment rank.
 9. The method of claim 7 wherein the firstcommunication station is a base station (BS) and the secondcommunication station is a wireless transmit/receive unit (WTRU). 10.The method of claim 7 wherein the first communication station is awireless transmit/receive unit (WTRU) and the second communicationstation is a base station (BS).
 11. A method for controllingtransmission power levels of signals in a spread spectrum time divisionduplex (TDD) communication system, the signals having frames with timeslots for providing a communication, the method comprising: (a) a firstcommunication station transmitting a first signal having a transmissionpower level in a first time slot; (b) a second communication stationreceiving the first communication and measuring a plurality of signalquality parameters of the first communication, the parameters includingat least one of a weighted signal interference information value, aweighted code usage estimation value and a weighted fading lossestimation value; (c) determining a slot assignment rank for the firstcommunication station based on the parameters; and (d) assigning asecond time slot to the first communication station for subsequentcommunications.
 12. The method of claim 11 further comprising: (e)prioritizing a plurality of wireless transmit/receive units (WTRUs)currently communicating via a communication network; and (f) assigningeach of said plurality of WTRUs a slot assignment based upon the slotassignment rank.
 13. The method of claim 11 wherein the firstcommunication station is a base station (BS) and the secondcommunication station is a wireless transmit/receive unit (WTRU). 14.The method of claim 11 wherein the first communication station is awireless transmit/receive unit (WTRU) and the second communicationstation is a base station (BS).
 15. In a spread spectrum time divisionduplex (TDD) communication system, a base station (BS) for controllingtransmission power levels of signals, the signals having frames withtime slots for providing a communication, the base station comprising:(a) means for receiving, in a first time slot, a first communicationhaving a transmit power level; (b) means for measuring a plurality ofsignal quality parameters of the first communication; (c) means forassigning a second time slot for transmission of a second communicationbased on the plurality of signal quality parameters; and (d) means fortransmitting the second communication in the second time slot.
 16. In aspread spectrum time division duplex (TDD) communication system, a basestation (BS) for controlling transmission power levels of signals, thesignals having frames with time slots for providing a communication, thebase station comprising: (a) means for receiving, in a first time slot,a first communication having a transmit power level; (b) means formeasuring a plurality of signal quality parameters of the firstcommunication, the parameters including at least one of a block errorrate (BLER) value and a signal to interference ratio (SIR) value; (c)means for assigning a second time slot for transmission of a secondcommunication based on the plurality of signal quality parameters; and(d) means for transmitting the second communication in the second timeslot.
 17. In a spread spectrum time division duplex (TDD) communicationsystem, a base station (BS) for controlling transmission power levels ofsignals, the signals having frames with time slots for providing acommunication, the base station comprising: (a) means for receiving, ina first time slot, a first communication having a transmit power level;(b) means for measuring a plurality of signal quality parameters of thefirst communication, the parameters including at least one of a weightedsignal interference information value, a weighted code usage estimationvalue and a weighted fading loss estimation value; (c) means forassigning a second time slot for transmission of a second communicationbased on the plurality of signal quality parameters; and (d) means fortransmitting the second communication in the second time slot.
 18. In aspread spectrum time division duplex (TDD) communication system, awireless transmit/receive unit (WTRU) for controlling transmission powerlevels of signals, the signals having frames with time slots forproviding a communication, the base station comprising: (a) means forreceiving, in a first time slot, a first communication having a transmitpower level; (b) means for measuring a plurality of signal qualityparameters of the first communication; (c) means for assigning a secondtime slot for transmission of a second communication based on theplurality of signal quality parameters; and (d) means for transmittingthe second communication in the second time slot.
 19. In a spreadspectrum time division duplex (TDD) communication system, a wirelesstransmit/receive unit (WTRU) for controlling transmission power levelsof signals, the signals having frames with time slots for providing acommunication, the base station comprising: (a) means for receiving, ina first time slot, a first communication having a transmit power level;(b) means for measuring a plurality of signal quality parameters of thefirst communication, the parameters including at least one of a blockerror rate (BLER) value and a signal to interference ratio (SIR) value;(c) means for assigning a second time slot for transmission of a secondcommunication based on the plurality of signal quality parameters; and(d) means for transmitting the second communication in the second timeslot.
 20. In a spread spectrum time division duplex (TDD) communicationsystem, a wireless transmit/receive unit (WTRU) for controllingtransmission power levels of signals, the signals having frames withtime slots for providing a communication, the base station comprising:(a) means for receiving, in a first time slot, a first communicationhaving a transmit power level; (b) means for measuring a plurality ofsignal quality parameters of the first communication, the parametersincluding at least one of a weighted signal interference informationvalue, a weighted code usage estimation value and a weighted fading lossestimation value; (c) means for assigning a second time slot fortransmission of a second communication based on the plurality of signalquality parameters; and (d) means for transmitting the secondcommunication in the second time slot.
 21. An integrated circuit (IC)for controlling transmission power levels of signals in a spreadspectrum time division duplex (TDD) communication system, the signalshaving frames with time slots for providing a communication, the ICcomprising: (a) means for receiving, in a first time slot, a firstcommunication having a transmit power level; (b) means for measuring aplurality of signal quality parameters of the first communication; (c)means for assigning a second time slot for transmission of a secondcommunication based on the plurality of signal quality parameters; and(d) means for transmitting the second communication in the second timeslot.
 22. An integrated circuit (IC) for controlling transmission powerlevels of signals in a spread spectrum time division duplex (TDD)communication system, the signals having frames with time slots forproviding a communication, the IC comprising: (a) means for receiving,in a first time slot, a first communication having a transmit powerlevel; (b) means for measuring a plurality of signal quality parametersof the first communication, the parameters including at least one of ablock error rate (BLER) value and a signal to interference ratio (SIR)value; (c) means for assigning a second time slot for transmission of asecond communication based on the plurality of signal qualityparameters; and (d) means for transmitting the second communication inthe second time slot.
 23. An integrated circuit (IC) for controllingtransmission power levels of signals in a spread spectrum time divisionduplex (TDD) communication system, the signals having frames with timeslots for providing a communication, the IC comprising: (a) means forreceiving, in a first time slot, a first communication having a transmitpower level; (b) means for measuring a plurality of signal qualityparameters of the first communication, the parameters including at leastone of a weighted signal interference information value, a weighted codeusage estimation value and a weighted fading loss estimation value; (c)means for assigning a second time slot for transmission of a secondcommunication based on the plurality of signal quality parameters; and(d) means for transmitting the second communication in the second timeslot.